Diethynylated phenylbenzimidazole compounds

ABSTRACT

A diethynylated phenylbenzimidazole compound having the formula: ##STR1## where Y is phenyl, cyclohexyl, adamantyl or phenoxylatedphenyl of the formula C 6  H 5  (OC 6  H 4 )n (n=1 to 3) and where R1, R2 and R3 are ethynyl, phenoxyethynyl, phenylethynyl, or hydrogen, and further wherein at least one of said R1, R2 or R3 is not hydrogen. The compounds can be cured to form thermoset polymers which are stable at temperatures above 300° C.

This is a division of application Ser. No. 655,009, filed Sept. 26,1984, now U.S. Pat. No. 4,537,974.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to high temperature, thermosetpolymers. More particularly, the present invention relates to newethynylated phenylbenzimidazole compounds, their use as prepolymers andtheir fabrication into polymer structures which are stable at hightemperatures.

2. Description of the Background Art

In the past two decades there has been a great deal of interest indeveloping heterocyclic polymers which have sufficient thermo-oxidativestability to be useful at temperatures up to 371° C. (700° F.). Althoughmany types of these high temperature polymers have been developed, mostof them have not been sucessfully utilized in the production of hardwareor produced on a commercial scale. The lack of commercialization ofthese polymers is due mainly to difficulties in processing. Generally,such polymers are highly intractable and cannot be effectively used infabrication. Even when made in prepolymer form, they still pose theproblem of generally liberating gaseous by-products when they undergofurther polymerization by condensation.

Five typical polymers of the general type mentioned above are:poly[benzobis(triazolo)phenanthroline];poly[(7-oxo-7,1OH-benz[d,e]imidazo[4',5':5,6]benzimidazo[2,1a]isoquinoline-3,4,10,11-tetryl)-10-carbonyl](commonly called BBL); poly[bis(benzimidazo)benzophenanthroline](commonly called BBB); polybenzimidazoquinazoline (generally referred toas PIQ); and polynaphthalimide. These materials represent some of themost stable polymers known. Other heterocyclic polymers such aspolybenzoxazoles, polybenzimidazoles, and polybenzothiazoles are alsowell documented in the polymer literature and have been shown to haveexcellent thermal stability.

The preparation of thermosetting prepolymers of the above-discussedgeneral classes of materials and the development of addition curingmechanisms for their polymerization could eventually provide usefulcommercial products. Their thermal stabilities are sufficiently close toeach other that it would be very difficult to predict accurately whichclass would ultimately give the most useful thermoset resins, since manyother variables must be considered. Accordingly, there is a continuingneed to develop additional monomers which can be conveniently processedby commercial fabrication techniques into polymers which exhibit thehigh temperature stability of the above-mentioned compounds.

Various acetylene-substituted compounds have been shown tohomopolymerize by the application of heat or a catalyst to form resinswhich are stable at high temperatures. As a result, practicalthermosetting acetylene-substituted prepolymers have begun to appear inthe literature. These acetylene-terminated prepolymers have shownpromise since they provide high-temperature thermosets which curewithout the evolution of gaseous by-products and could eventually yieldfabricated structures having excellent thermal and mechanicalproperties. However, the early introduction of an acetylene-substitutedresin, Haveg-H-resin (Hercules, Inc.), met with very limited success,mainly because of the relatively small processing window and the poorlong-term high-temperature oxidative stability of the cured product.

Thermosetting polyimide oligomers have also been considered as possibleuseful high temperature resins due to the excellent thermal stabilityinherent in the polyimide backbone. A series of acetylene-terminatedpolyimide prepolymers has been developed which is soluble in anacceptable common solvent and tractable in imidized form. Theseprepolymers were subsequently marketed as Thermid 600 by Gulf Oil andChemical Company.

Other acetylene or ethynyl terminated oligomers such asacetylene-terminated phenylquinoxalines have been under development.These prepolymers are also thermosetting and can be cured to providemoisture-resistant products of very high thermo-oxidative stability. Theoligomers have many properties desirable for processing, i.e., highsolubility in low-boiling-point aprotic solvents, low softeningtemperature prior to cure, a wide temperature difference between themelting and cure temperatures, cure without the evolution of gaseousproducts, and after cure, glass transition temperature sufficiently high(310°-350° C.) to allow long-term use at 250° C. Relative advantages ofthe various types of acetylene-terminated polyquinoaxlines have not beenfully determined, although mechanical property data have been collected.

Another acetylene-terminated prepolymer which is receiving considerableattention is bis[4-(3-ethynylphenoxy)phenyl]sulfone. This material hasbeen evaluated as a polymerizable plasticizer for variousthermoplastics.

As is apparent from the discussion above, numerous differentacetylene-terminated monomers have been developed which are suitable invarying degrees for use in fabricating high temperature resins. Even so,there is still a continuing need to develop new classes ofacetylene-terminated compounds which are easily and convenientlyfabricated to provide addition-curing processible matrix resins having aservice temperature capability of 350° C.

SUMMARY OF THE INVENTION

In accordance with the present invention, a new benzimidazole monomercompound has been discovered which can be processed into hightemperature polyphenylbenzimidazole polymers which are stable attemperatures above 300° C.

The present invention is based on a diethynylated bisbenzimidazolemonomer having the formula: ##STR2## where Y is phenyl, cyclohexyl,adamantyl or phenoxylatedphenyl of the formula C₆ H₅ (OC₆ H₄)n (n=1 to3) and where R1, R2 and R3 are ethynyl, phenoxyethynyl, phenylethynyl orhydrogen.

As one aspect of the present invention, a prepolymer, which consistsessentially of oligomers of compounds in accordance with the presentinvention, is provided which may be heat cured to provide a polymerproduct which is easily fabricated and remains stable at relatively hightemperatures. The invention also includes the polymers produced eitherdirectly from the monomer or by way of a prepolymer.

The present invention provides a new benzimidazole monomer and oligomercompositions which are more tractable and easier to handle and processthan prior high temperature resin precursors, while still providing apolymer product having good high temperature stability.

The above-discussed and many other features and attendant advantages ofthe present invention will become apparent as the invention becomesbetter understood by reference to the following detailed descriptionwhen considered in conjunction with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING

The drawing is a schematic outline of the synthesis of an exemplarypreferred compound in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention involves the synthesis of a new benzimidazolemonomer having the general formula: ##STR3## where Y is pheynl,cyclohexyl, adamantyl or phenoxylatedphenyl of the formula C₆ H₅ (OC₆H₄)n (n=1 to 3) and R1, R2 and R3 are ethynyl, phenyoxyethynyl,phenylethynyl or hydrogen.

Preferably, only one of R1, R2 or R3 is ethynyl or an ethynyl derivativefor a given compound with the two other remaining R groups beinghydrogen. Although compounds in accordance with the present inventioninclude those having ethynyl groups at both the para- andmeta-positions, these compounds are more difficult to make than thosehaving only a single ethynyl, phenyoxyethynyl or phenylethynyl groupattached at the meta (R1 and R3) or para (R2) positions. Accordingly,the following description will be limited to those monomers in whichhydrogen is present at two of the three R1, R2 and R3 positions.

A preferred monomer is one in which R1 or R3 is ethynyl and theremaining two R groups (i.e., either R1 or R3, and R2) are hydrogen andY is phenyl. Preparation and use of this preferred compound is shown inthe drawing and discussed in detail below. In another preferredcompound, the ethynyl group is positioned at the para-position (R2)instead of the meta-position (R1 or R3). Preparation of this compound isalso set forth in the following examples.

In addition to phenyl groups, bridged compounds such as adamantane maybe incorporated into the monomer by attachment as an adamantyl group atthe Y position to increase the rigidity of the polymer product and toenhance the basicity of the nitrogen atom to which the adamantyl groupis attached. Saturated cycloalkanes, such as cyclohexane may be attachedat the Y position as well as phenoxylated phenyl pendants of the formulaC₆ H₄ (OC₆ H₄)n (n=1, 2, or 3). It is preferred that n=1; however, whendesired to provide added flexibility to the polymer, 2 or 3phenyoxyphenyl groups may be attached at the Y site (i.e., n=2 or 3).

The monomers in accordance with the present invention may be handled inaccordance with conventional fabrication and processing techniques usedfor polybenzimidazole (PBI) and other thermoset polymers. Preferably,prepolymer solutions consisting essentially of oligomers of the monomerare prepared and then heat cured according to conventional techniques toprovide a polymer product which is useful as a high temperature polymer.The polymer products have been shown to be stable at temperatures above300° C.

Examples of practice are as follows.

EXAMPLE 15,5'-(hexafluoroisopropylidine)bis[1-phenyl-2-(3-ethynylphenyl)benzimidazole](Compound VIII)

The synthesis of Compound VIII as an exemplary compound in accordancewith the present invention is schematically shown in the drawing. Thesynthesis basically involves a condensation reaction between3-(trimethylsilylethynyl)benzaldehyde (VI) and2,2-bis(3-amino-4-anilinophenyl)hexafluoropropane (V).

EXAMPLE 1A 3-(trimethylsilylethynyl)benzaldehyde (Compound VI)

Compound VI was synthesized by the organopalladium-catalyzedethynylation of meta-bromobenzaldehyde with ethynyltrimethylsilane asfollows: ##STR4##

The details of preparation of compound VI are set forth in a publicationby W. B. Austin, N. Bilow, W. J. Kelleghan and K. S. Y. Lau in theJournal of Organic Chemistry, Vol. 46, p. 2280 et seq., (1981), thecontents of which is hereby incorporated by reference. The compound (VI)was synthesized with an 80% yield and had the following properties: bp120°-122° C./0.15 torr; IR (film): 2958, 2146, 1692, 1244, and 843 cm⁻¹; MS m/e 202 (molecular ion), 187; NMR (CDCl₃): δ0.22 (s, 9H, SiCH₃),7.15-9.93 (m, 4H, aromatic), and 9.85 ppm (s, 1H, CHO).

Analysis: Calculated for C₁₂ H₁₄ OSi: C, 71.24%: H, 7.33%; Si, 13.88%.Found: C, 71.10%; H, 7.07%; Si, 14.04%.

Nuclear magnetic resonance (NMR) spectra were taken on a Varian EM-360Lspectrometer with tetramethylsilane (TMS) as the internal standard.Infrared (IR) spectra were taken on a Beckman IR-5 spectrometer. Massspectra (MS) were measured by West Coast Technical Service, Inc.,Cerritos, Calif. Elemental anaylses were performed by GalbraithLaboratories, Knoxville, Tenn.

EXAMPLE 1B 2,2-Bis(3-amino-4-anilinophenyl)hexafluoropropane (CompoundV)

Compound V was prepared from 2,2-bis(4-hydroxyphenyl)hexafluoropropane(I) according to the four-step synthetic sequence outlined in thedrawing. The details of the synthesis are set forth in an article by K.S. Y. Lau, A. L. Landis, W. J. Kelleghan, and C. D. Beard in the Journalof Polymer Science, Polymer Chemistry Edition, Vol, 20, p. 2381 et seq.,(1982), the contents of which is hereby incorporated by reference. Anoverall yield of 89.3% was obtained with the compound having thefollowing properties:

Mp 120° C.; IR (KBr): 3380 (strong, broad, NH₂), 1620, 1600, 1520, 1500(strong, sharp, C═N and C═C), and 1310-1160 cm⁻¹ (strong, very broad,CF₃); NMR (acetone-d₆): δ2.90 (bs, 3H, NH) and 6.35-7.42 ppm (m, 8H,aromatic).

Analysis: Calculated for C₂₇ H₂₂ F₆ N₄ : C, 62.79%; H, 4.29%; N, 10.85%;F, 22.01%. Found: C, 62.61%; H, 4.26%; N, 10.70%; F, 22.15%.

EXAMPLE 1C5,5'-(hexafluoroisopropylidene)bis[1-phenyl-2-(3-ethynylphenyl)benzimidazole](Compound VIII)

Compound VIII was synthesized from compounds (VI) and (V) as follows. Amixture of 2.00 g of sodium metabisulfite and 0.76 g (4.26 mmol) of3-(trimethylsilylethynyl)benzaldehyde (VI) in 50 ml of 1:1 ethanol-waterwas deaerated with argon and heated at 75°-80° C. for 30 minutes. Theyellow solution was then treated with a slurry of 1.00 g (1.94 mmol) of2,2-bis(3-amino-4-anilinophenyl)hexafluoropropane (V) in 50 ml ofethanol. The mixture was heated at a gentle reflux (oil bath temperatureabout 100° C.) for 7 hours, cooled, diluted with 100 ml of 10%hydrochloric acid. The bright yellow solid was filtered, then washedwith 50 ml of 10% hydrochloric acid, 50 ml of water and 50 ml of coldhexane. The powdery product (VII), after thorough drying, weighed 1.67 g(1.90 mmol, 97.8%) and showed characteristic trimethylsilylethynylabsorptions in its infrared spectrum.

The above product (VII) (1.36 g, 1.55 mmol) was treated with 100 mg ofanhydrous potassium carbonate in 50 ml of methanol under argon for 24hours. The mixture was concentrated, dissolved in 50 ml dichloromethane,and washed with 50 ml of 10% hydrochloric acid. The organic phase wasdried over magnesium sulfate and concentrated; the residue wastriturated with cold hexane to yield 1.02 g (1.39 mmol, 89.5%) of apowdery solid. The product was purified by column chromatography using1:1 dichloromethane-hexane as eluant. Infrared spectra indicated IR(KBr): 3500-3000, 3300, and 2120 cm⁻¹.

EXAMPLE 2 Scaled up Synthesis of5,5'-(hexafluoroisopropylidene)bis[1-phenyl-2-(3-ethynylphenyl)benzimidazole](Compound VIII)

Synthesis of the above compound (VIII) was scaled up to aquarter-molar-scale to demonstrate the feasibility of larger scaleproduction. Except for the scaleup proportions, the procedure as setforth below, was identical to the synthesis described above.

A mixture of 115 g (0.570 mol) of 3-(trimethylsilylethynyl)benzaldehydeand 216 g (1.14 mol) of sodium metabisulfite in 2 L of 1:1 ethanol-waterwas heated at 70°-80° C. for 1 hour and mixed with 110.6 g (0.214 mol)of 2,2-bis(3-amino-4-anilinophenyl)hexafluoropropane in 1 L of ethanol.The mixture was stirred at reflux for 24 hours. The mixture aftercooling was diluted with 6 L of 5% aqueous hydrochloric acid.Filtration, washing with water, and thorough drying yielded a total of182.5 g (0.207 mol, 96.9%) of a powdery solid which showed thecharacteristic infrared absorptions for the trimethylsilylethynylgroups.

The crude product was dissolved in 1.5 L of absolute methanol andtreated with 10 g of anhydrous potassium carbonate. The initial darkbrown solution slowly yielded a yellowish precipitate. After beingstirred for 60 hours at 25° C., the mixture was diluted with an equalvolume of 5% hydrochloric acid and filtered, and the solid was air driedthoroughly.

The first crop (90 g crude yield) was filtered through a preparativecolumn of silica gel with 2:1 hexane-dichloromethane as eluant. Thecolumn-purified end product was pale yellow and powdery and gave acombustion analysis acceptable for the desired prepolymer. Infraredanalysis showed the characteristic ethynyl end groups (3300, 2120 cm⁻¹).

Analysis: Calculated for C₄₅ H₂₆ F₆ N₄.H₂ O: C, 71.61%; H, 3.74%; F,15.10%; N, 7.42%. Found: C, 71.75%; H, 3.86%; F, 14.92%; N, 7.37%.

The observed gel time at 250° C. on the Kofler hot bench wassignificantly shorter (about 1 minute) for the scaleup batch than forthat synthesized on a small scale (3-4 minutes). Thin-layerchromatography suggested that higher oligomers were present. Washing ofthe column-purified powder with ether separated the ether-insolubleportion, which was probably mostly higher oligomeric material. Nomelting was observed even at 275° C. The ether-soluble portion gave anobserved gel time at 250° C. of about 1 minute.

EXAMPLE 3 Alternate method of synthesizing5,5'-(hexafluoroisopropylidene)bis[1-phenyl-2-(3-ethynylphenyl)benzimidazole](Compound VII)

An alternate method of synthesizing Compound VII is as follows. Asolution of 6.0 g of sodium metabisulfite in 75 ml of water was mixedwith 2.58 g (14.0 mmol) of 3-(trimethylsilylethynyl)benzaldehyde (VI) in125 ml of ethanol, deaerated with argon, and heated to reflux over 15minutes. The mixture was heated at reflux for 30 minutes and thentreated by dropwise addition with a solution of 3.00 g (5.81 mmol) of2,2-bis(3-amino-4-anilinophenyl)hexafluoropropane (V) in 250 ml ofethanol. After complete addition (1 hour), the mixture was heated atreflux for 24 hours. The mixture was then cooled, stirred into 1 L of10% hydrochloric acid, and filtered. The powdery solid (VII) afterthorough drying, weighed 5.10 g (5.80 mmol, 99.7%). Characteristicinfrared absorptions of the trimethylsilylethynyl groups were exhibited.

The crude product (VII) was treated with 1 g of anhydrous potassiumcarbonate in 100 ml of methanol at 25° C. for 24 hours. The solvent wasremoved and the residue thoroughly washed with 10% hydrochloric acid andair dried. The powdery end product (VIII) was washed with ether to yieldether-soluble and ether-insoluble fractions. The ether-insolublefraction did not melt at 250° C. The ether-soluble fraction gave alustrous yellow powdery material; yield 2.5 g (58.4%); at 230°, 240°,and 250° C., this material melted to a fluid which resolidified in about3 minutes. The ether-soluble and the ether-insoluble fractions havesuperimposable IR spectra showing the characteristic ethynyl end-groupabsorptions (3300, 2100 cm⁻¹).

The exact procedure described above (high dilution and dropwiseaddition) was repeated for 26.0 g of the aldehyde (VI), 110 g of sodiumbisulfite, and 30.0 g of the tetramine (V) in a total volume of 4.5 L of1:5 water-ethanol. At the end, the powdery end product (VIII) wasfractionated by Soxhlet extraction into an ether-insoluble portion (higholigomers) and an ether-soluble portion (20.0 g, 46.9%). The lattermaterial, when tested on the Kofler hot bench at 250° C., showed a geltime of about 3 minutes.

EXAMPLE 45,5'(hexafluoroisopropylidene)bis[1-phenyl-2-(4-ethynylphenyl)benzimidazole](Compound IX)

Compound IX was prepared as a second exemplary compound in accordancewith the present invention. Compound IX is the same as compound VIIIexcept that the ethynyl groups are located at the para-position insteadof the meta-position as indicated in the following structural formula:##STR5##

Preparation of compound IX is basically the same as preparation ofcompound VIII except that 4-(trimethylsilylethynyl)benzaldehyde is usedin the condensation reaction instead of3-(trimethylsilylethynyl)benzaldehyde (VI).

EXAMPLE 4A 4-(trimethylsilylethynyl)benzaldehyde

Preparation of 4-(trimethylsilylethynyl)benzaldehyde is described indetail in the previously referenced article and is basically the same asthe preparation of compound (VI) described herein, except thatpara-bromobenzaldehyde is ethynylated. The4-(trimethylsilylethynyl)benzaldehyde for this example was preparedaccording to the above-referenced procedure and provided a 99% yield.The physical properties of the compound were:

Mp 66°-67° C.; IR (KBr): 2960, 2825, 2720, 2145, 1690, 1245, and 840cm⁻¹, MS m/e 202 (molecular ion), 187; NMR (CDCl₃): 0.21 (s, 9H,Si═CH³), 7.60 (q, 4H, J=7.0 Hz, aromatic), and 9.85 ppm (s, 1H, CHO).

Analysis: Calculated for C₁₂ H₁₄ OSi: C, 71.24%; H, 7.33%; Si, 13.88%.Found: C, 71.31%; H, 7.42%; Si, 14.01%.

EXAMPLE 4B5,5'(hexafluoroisopropylidene)bis[1-phenyl-2-(4-ethynylphenyl)benzimidazole](Compound IX)

A mixture of 0.64 g (3.20 mmol) of 4-(trimethylsilylethnyl)benzaldehydeand 1.98 g of sodium metabisulfite in 25 ml deionized water and 30 mlethanol was deaerated with argon, heated to about 75° C., and held atthat temperature for 30 minutes. A solution of 0.83 g (1.61 mmol) of2,2-bis(3-amino-4-anilinophenyl)hexafluoropropane (V) in 35 ml ofethanol was added dropwise. The resulting mixture was heated at 75° C.for 6.5 hours and at 90° C. for 3 hours, cooled, and diluted with 50 mlof water. The solids isolated were extracted with 3×100 ml of hexane;the extracts were combined and washed with 10% hydrochloric acid andthen with water. After drying over magnesium sulfate, the solution wasconcentrated to yield a bright yellow compound which softened at about140° C. and melted at about 200° C. Infrared analysis indicatedcharacteristic absorptions due to the trimethylsilylethynyl groups(3000, 2160, 1200, 850 cm⁻¹).

The crude product was treated with 100 mg of anhydrous potassiumcarbonate in 100 ml of methanol under argon. After being stirred for 16hours, the mixture was concentrated and the residue was dissolved in 50ml dichloromethane and extracted with 50 ml of 5% hydrochloric acid. Theorganic phase was dried over magnesium sulfate, concentrated, andpurified by column chromatography on silica gel, using 1:1dichloromethanehexane as eluant. The off-white microcrystalline solid(IX) weighed 1.10 g (1.49 mmol, 92.6%); m; 265° C. (melted andresolidified within seconds); IR (KBr): 3500-3000 and 2120 cm⁻¹.

Analysis: Calculated for C₄₅ H₂₆ F₆ N₄.H₂ O: C, 71.61%; H, 3.74%; F,15.10%; N, 7.42%. Found: C, 71.57%; H, 3.89%; F, 15.15%; N, 7.38%.

EXAMPLE 55,5'-(hexafluoroisopropylidene)bis[1-(4-phenoxyphenyl)-2-(3-ethynylphenyl)benzimidazole](Compound X)

Compound X was prepared as a third exemplary compound in accordance withthe present invention. The compound is the same as compound VIII exceptthat phenoxyphenyl is substituted for phenyl on the imidazole group(Y=phenoxyphenyl and n=1), as indicated in the following structuralformula: ##STR6##

Compound (X) was prepared as follows.

A deaerated mixture of 4.75 g (25.0 mmol) of sodium metabisulfite and2.04 g (10.0 mmol) of 3-(trimethylsilylethynyl)benzaldehyde (VI) in 150ml of 50% aqueous ethanol was heated to 75° C. over 15 minutes. Asolution of 3.20 g (4.58 mmol) of2,2-bis[3-amino-4-(4-phenoxyanilino)phenyl]hexafluoropropane (XI) in 90ml of absolute ethanol was added dropwise from an addition funnel whilethe reaction mixture was stirred at 80°-85° C. Details of thepreparation of compound XI are also set forth in the article which waspreviously referenced in connection with the preparation of compound V.

The addition was controlled carefully so that it took 1.5 hours tocomplete. At the end, 50 ml more of ethanol was added. The mixture wasstirred under argon at 85°-90° C. for 1 hour. After 48 hours, thereaction mixture was cooled and was treated with 250 ml of 10%hydrochloric acid. The milky suspension was extracted with 4×100 ml ofdichloromethane. The combined dichloromethane extracts were washed with150 ml of water containing 10 g of sodium bicarbonate, and with 150 mlof water, and then were dried over magnesium sulfate. Removal of thesolvent left a light brown oil which, upon trituration with hexane, gavea pale yellow solid. NMR analysis of a solution of this product inacetone-d₆ showed that the ratio of SiCH₃ (δ0.1 ppm) to aromatic(δ6.80-8.00 ppm) was 19.7/34.3(0.57), which agreed with the theoreticalvalue of 18/32(0.56). Infrared analysis showed the expected absorptionscharacteristics of trimethysilyl groups (2960, 2160, 1250, and 840cm⁻¹). The pale yellow solid obtained was dissolved in 40 ml ofanhydrous methanol, to which 1 g of anhydrous potassium carbonate wasthen added. The mixture was stirred at 25° C. for 24 hours before beingtreated with 50 ml of 10% hydrochloric acid. The gummy precipitateobtained was vigorously agitated until it appeared powdery. The solidwas filtered and recrystallization from 50 ml of 1:2dichloromethanehexane; yield 3.04 g (72.5% from the tetraamine). Theproduct was further purified by column chromatography through a silicagel column, eluting with dichloromethane. Infrared spectra indicated IR(KBr): 3450, 3310, (strong C.tbd.CH), 3080, 2160 (weak C.tbd.C), 1590,1510, 1490, and 1250-1200 cm⁻¹ ; NMR (Acetone-d₆): δ3.60 (2H, C.tbd.CH),and 6.95-8.00 ppm (m, 32H, aromatic).

Analysis: Calculated for C₅₇ H₃₄ N₄ F₆ O₂.H₂ O): C, 72.92%; H, 3.94%; F,12.14%; N, 5.97%. Found: C, 72,82%; H, 3.74%; F, 12.27%; N, 5.78%.

The melt behavior of the product was observed on the Kofler hot bench.Melting was observed at a temperature as low as 150° C. The gel timesmeasured on milligram batches were 4 minutes at 210° C., 5 minutes at170° C., 6.5 minutes at 160° C., and 10.5 minutes at 150° C.

EXAMPLE 6 Polymerization of prepolymers

Examples of preparation and fabrication of prepolymers and polymers fromthe above-described compounds are as follows.

A first large batch (quarter-molar scale) of prepolymer (VIII) wassynthesized as previously described. This first scaleup of compoundVIII, as also previously mentioned, had a short gel time (1 minute). Thematerial had IR, NMR, and combustion analyses that wereindistinguishable from the previously prepared smaller batch of VIII, soit was concluded that either higher-molecular-weight oligomeric materialwas present in the scaleup product or that there was an undefinedoperator variable.

In order to reduce the quantity of this oligomeric material, if it wasin fact present, the condensation reaction of compound V with aldehydewas rerun at higher dilution as set forth in the alternate method forpreparing compound VIII (supra). Subsequent conversion of this secondbatch of compound VIII resulted in a quite acceptable prepolymer, basedupon its significantly longer gel time.

Preliminary neat resin gel time studies and prepreg fabrication wereperformed on prepolymers VIII. The first batch (from the small scalesynthesis) of VIII showed an initial melting range of 225°-230° C., andchanged to a molasses-like consistency, remaining soft for 6-8 minutesbefore hardening into the cured polymer. The latter remelted to a fluidat 240° C. At 246°-250° C., the fluid hardened within 4.5-5.0 minutes.At 260° C., the gel time was 3.5 minutes. The neat resin was molded intobutton specimens. The specific gravity was measured to be 1.28. Theglass transition temperature (Tg) after 16-hour postcure at 316° C. was311° C.; Tg after 16-hour postcure at 371° C. was 344° C.

The results of gel time studies on the first scaleup batch of VIII were2.5-3.0 minutes at 250° C. and 1.5 minutes at 260° C., which indicatedthat this batch contained oligomers of higher degree of polymerization(DP) than the previous batch.

The N-phenoxy-substituted diethynylated bisbenzimidazole prepolymer (X)showed good potential processibility. On the temperature-calibrated hotbench, it became fluid at temperatures below 170° C. and, at thesetemperatures, appeared to remain fluid for about 8-10 minutes. An 8 gbatch of prepolymer (X) was prepared for preliminary neat resinevaluation. This batch of material began to soften at a temperature aslow as 116° C. At 170° C., it developed a molasses-like consistency andremained soft over 8 minutes. At 200° C., it melted to a fluid, remainedfluid over 8 minutes, and resolidified after 10 minutes. At 250° C., itmelted to a fluid and resolidified within 3.5 minutes. At 261° C., itstill had a gel time of 35-45 seconds. After prepolymer (X) was furtherpurified by column chromatography, it became a fluid even below 170° C.and rehardened after 10 minutes. The polymer of (X) appears slightlysoluble in acetone after a short (40±5 seconds) "cure" at 261° C.; itwas very slightly soluble in acetone after 4 hours at 316° C., and wasinsoluble in acetone after 14 hours at 320° C. Although an 8 minute geltime at 200° C. is an encouraging result, the fact that thepolymerization exotherm reaches a maximum at 235° C. indicates thatreal-time processing will have to be carried out at a temperature of235° C. or higher at which temperature the gel time is much shorter. Theprocessing characteristics of prepolymer (X) appear to be better thanthose for prepolymers made from compound VIII. Accordingly, the (X)prepolymer is a preferred embodiment.

Having thus described exemplary embodiments of the present invention, itshould be noted by those skilled in the art that the within disclosuresare exemplary only and that various other alternatives, adaptations andmodifications may be made within the scope of the present invention.Accordingly, the present invention is not limited to the specificembodiments as illustrated herein, but is only limited by the followingclaims.

What is claimed is:
 1. A polymer composition consisting essentially ofpolymerized monomers having the formula: ##STR7## where Y is phenyl,cyclohexyl, adamantyl or phenoxylatedphenyl of the formula C₆ H₅ (OC₆H₄)n (n=1 to 3) and where R1, R2 and R3 are ethynyl, phenoxyethynyl,phenylethynyl or hydrogen, and further wherein at least one of said R1,R2 or R3 is not hydrogen.
 2. A polymer composition according to claim 1wherein R1 is hydrogen, R2 is hydrogen, R3 is ethynyl, Y isphenoxylatedphenyl, and n=1.
 3. A polymer composition according to claim1 wherein R1 is hydrogen, R2 is hydrogen, R3 is ethynyl, and Y isphenyl.